They were subject to error, but Paul simply calls this the day of Christ's coming for his people, the Church.
Speaking of the phrase "the day of Christ"... here's a post I'd made about the phrasing
in v.2 (the thing that the false conveyors were
purporting "
IS ALREADY HERE / IS PRESENT [PERFECT INDICATIVE]"):
[LISTING from BibleHub--23 Versions having it as "day of the Lord" i.e. the EARTHLY-LOCATED time-period (not "day of Christ"--when WE will be UP THERE *with HIM*)]
New International Version
not to become easily unsettled or alarmed by the teaching allegedly from us--whether by a prophecy or by word of mouth or by letter--asserting that
the day of the Lord has already come.
New Living Translation
Don’t be so easily shaken or alarmed by those who say that
the day of the Lord has already begun. Don’t believe them, even if they claim to have had a spiritual vision, a revelation, or a letter supposedly from us.
English Standard Version
not to be quickly shaken in mind or alarmed, either by a spirit or a spoken word, or a letter seeming to be from us, to the effect that
the day of the Lord has come.
Berean Study Bible
not to be easily disconcerted or alarmed by any spirit or message or letter seeming to be from us, alleging that
the Day of the Lord has already come.
New American Standard Bible
that you not be quickly shaken from your composure or be disturbed either by a spirit, or a message, or a letter as if from us, to the effect that
the day of the Lord has come.
NASB 1995
that you not be quickly shaken from your composure or be disturbed either by a spirit or a message or a letter as if from us, to the effect that
the day of the Lord has come.
NASB 1977
that you may not be quickly shaken from your composure or be disturbed either by a spirit or a message or a letter as if from us, to the effect that
the day of the Lord has come.
Amplified Bible
not to be quickly unsettled or alarmed either by a [so-called prophetic revelation of a] spirit or a message or a letter [alleged to be] from us, to the effect that
the day of the Lord has [already] come.
Christian Standard Bible
not to be easily upset or troubled, either by a prophecy or by a message or by a letter supposedly from us, alleging that
the day of the Lord has come.
Holman Christian Standard Bible
not to be easily upset in mind or troubled, either by a spirit or by a message or by a letter as if from us, alleging that
the Day of the Lord has come.
Good News Translation
not to be so easily confused in your thinking or upset by the claim that
the Day of the Lord has come. Perhaps it is thought that we said this while prophesying or preaching, or that we wrote it in a letter.
GOD'S WORD® Translation
Don't get upset right away or alarmed when someone claims that we said through some spirit, conversation, or letter that
the day of the Lord has already come.
International Standard Version
not to be so quickly upset or alarmed when someone claims that we said, either by some spirit, conversation, or letter that
the Day of the Lord has already come.
NET Bible
not to be easily shaken from your composure or disturbed by any kind of spirit or message or letter allegedly from us, to the effect that
the day of the Lord is already here.
New Heart English Bible
not to be quickly shaken in your mind, nor yet be troubled, either by spirit, or by word, or by letter as from us, saying that
the day of the Lord had come.
Darby Bible Translation
that ye be not soon shaken in mind, nor troubled, neither by spirit, nor by word, nor by letter, as [if it were] by us, as that
the day of the Lord is present.
English Revised Version
to the end that ye be not quickly shaken from your mind, nor yet be troubled, either by spirit, or by word, or by epistle as from us, as that
the day of the Lord is now present;
Literal Standard Version
that you are not quickly shaken in mind, nor be troubled, neither through spirit, neither through word, neither through letters as through us, as that
the Day of the LORD has arrived;
Berean Literal Bible
for you not quickly to be shaken in mind, nor to be troubled, neither by spirit, nor by word, nor by letter as if by us, as that
day of the Lord is present.
Aramaic Bible in Plain English
That you would not be soon shaken in your minds, neither be troubled, either from word, nor from a spirit, neither from an epistle that is as if from us, namely, that, “Behold,
The Day of our Lord has arrived.”
Godbey New Testament
that you be not suddenly shaken from your mind, nor disturbed, whether by a spirit, or through word, or a letter as by us, as that
the day of the Lord has come.
Weymouth New Testament
not readily to become unsettled in mind or troubled--either by any pretended spiritual revelation or by any message or letter claiming to have been sent by us--through fancying that
the day of the Lord is now here.
Worrell New Testament
that ye be not quickly shaken from your mind, nor be troubled, either by spirit, or by word, or by letter as from us, as that
the day of the Lord has set in.
...considering that they are
purporting that it "IS ALREADY HERE / IS PRESENT [
PERFECT INDICATIVE]," it would be a PERFECTLY REASONABLE thing for them to be [
wrongly] persuaded was TRUE [tho false],
because of their PRESENT and ONGOING, *
very negative* PERSECUTIONS and TRIBULATIONS they were already ONGOINGLY *enduring*
per 1:4... THAT made what the false conveyors were
purporting to be
COMPLETELY *BELIEVEABLE*.
The other suggestions ppl offer to what the false conveyors were purporting (v.2) are NOT things which REASONABLE people would be persuaded by, at least not for longer than about 3.5
MINUTES! You seem to be wanting me to think the Thessalonians were utter dunces,
even after Paul informs us that THEY "KNOW PERFECTLY" the manner of the ARRIVAL of "the DOTL" that it will be LIKE the INITIAL "birth PANG [SINGULAR; 1Th5:
2-3]" that COMES UPON a woman... (and yet they've suddenly *
forgotten* what they,
just a short time ago, "KNEW [KNOW] PERFECTLY"... what a laugh!
... I remain unconvinced of your viewpoint.)